Because it's a step in the process of making moon bases, and eventually Mars bases, asteroid bases, Jovian-moon bases, deep-space bases, and eventually interst

Because it's a step in the process of making moon bases, and eventually Mars bases, asteroid bases, Jovian-moon bases, deep-space bases, and eventually interstellar bases economically viable. The Earth is very small, and the universe is very large. Eventually, we're going to want to use more than an earth-sized corner of it. Why not start now?